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Re: [linux-lvm] Allocation Policy for Cloud Computing needed



On 20/02/12 22:59, Lars Ellenberg wrote:
>> Or does someone want to implement this together with me?
> 
> I would certainly be here for discussions.
> 
> Though, as you always will be more flexible with scripts than with
> pre-implemented fixed algorithms, I probably would first check if I can
> solve it with some scripting.
> [completely untested, but you get the idea]
> 
> #!/bin/bash
> export LANG=C LC_ALL=C
> name=$1 vg=$2 size_in_MiB=$3
> PVS=$(vgs --nohead --unit m -o pv_name,pv_free -O -pv_free,pv_name $vg |
> 	awk -v need=$size_in_MiB '{ print $1; sum += $2;
> 	if (sum >= need) exit; }')
> lvcreate -n $name -L ${size_in_MiB}m $vg $PVS
> 
> (similar for lvextend)
> 
> Which basically implements this allocation policy:
> use the pvs with most free space available,
> and no more than necessary.
> 
> If I understand you correctly, that would almost do what you asked for.

Yes, this really helps. I've also thought about allocating the LVs
directly to distinct PVs. Thanks for the confirmation.

> You can get pretty complex in similar scripts, if you really want to...
> consider using
>   pvs -o vg_name,lv_name,pv_name,pvseg_start,pvseg_size,seg_pe_ranges
> and explicitly listing not only the PVS, but even the PE ranges to your
> lvcreate commands...

Thank you very much for your response.

Regards,
Sebastian


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